Symmetrical organization of proteins under docked synaptic vesicles

During calcium‐regulated exocytosis, the constitutive fusion machinery is ‘clamped’ in a partially assembled state until synchronously released by calcium. The protein machinery involved in this process is known, but the supra‐molecular architecture and underlying mechanisms are unclear. Here, we us...

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Bibliographic Details
Published in:FEBS letters 2019-01, Vol.593 (2), p.144-153
Main Authors: Li, Xia, Radhakrishnan, Abhijith, Grushin, Kirill, Kasula, Ravikiran, Chaudhuri, Arunima, Gomathinayagam, Sujatha, Krishnakumar, Shyam S., Liu, Jun, Rothman, James E.
Format: Article
Language:English
Subjects:
Animals
Calcium - metabolism
Cryoelectron Microscopy
cryo‐electron tomography
Electron Microscope Tomography
Exocytosis
Munc18 Proteins - genetics
Munc18 Proteins - metabolism
Mutation
Nerve Growth Factor - pharmacology
Nerve Tissue Proteins - genetics
Nerve Tissue Proteins - metabolism
Neurites - drug effects
Neurites - metabolism
PC12 Cells
Rats
regulated exocytosis
Research Letter
Research Letters
SNARE proteins
SNARE Proteins - genetics
SNARE Proteins - metabolism
Synaptic Vesicles - chemistry
Synaptic Vesicles - genetics
Synaptic Vesicles - metabolism
synaptotagmin
Synaptotagmins - genetics
Synaptotagmins - metabolism
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Summary:During calcium‐regulated exocytosis, the constitutive fusion machinery is ‘clamped’ in a partially assembled state until synchronously released by calcium. The protein machinery involved in this process is known, but the supra‐molecular architecture and underlying mechanisms are unclear. Here, we use cryo‐electron tomography analysis in nerve growth factor‐differentiated neuro‐endocrine (PC12) cells to delineate the organization of the release machinery under the docked vesicles. We find that exactly six exocytosis modules, each likely consisting of a single SNAREpin with its bound Synaptotagmins, Complexin, and Munc18 proteins, are symmetrically arranged at the vesicle–PM interface. Mutational analysis suggests that the symmetrical organization is templated by circular oligomers of Synaptotagmin. The observed arrangement, including its precise radial positioning, is in‐line with the recently proposed ‘buttressed ring hypothesis’.
ISSN:0014-5793
1873-3468
DOI:10.1002/1873-3468.13316